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Summary of the impact

The transport of people, goods, and utilities (e.g. electricity, oil, gas
and water) is essential to
civilised life, and in turn depends on a robust, reliable and affordable
infrastructure. Since 1995, the
University of Southampton Geomechanics Group (SGG) has led the development
of an enhanced,
science-based framework for understanding the behaviour of geotechnical
transport infrastructure
through monitoring, modelling and analysis. The techniques we have
developed have been used
by the builders, owners and operators of transport infrastructure both
nationally and internationally
to develop improved understandings of infrastructure geotechnical
behaviour both during
construction and in service. This has led to substantial savings in build,
maintenance and
operational costs; the implementation of effective remediation and
management strategies; and
significantly improved infrastructure performance.

Underpinning research

In the mid-1990s, there was a perception within the construction industry
that the loads in props
used for the temporary support of large, deep excavations were
uncalculable. To investigate this,
Powrie (1995ff) and Richards (1995ff) developed methods for
the continuous, detailed monitoring
of prop loads, which we deployed during construction of the Jubilee Line
extension stations at
Canary Wharf and Canada Water, 1995-6 [3.1]. This gave a clear
understanding of how prop loads
and other structural stress resultants should be monitored if meaningful
data are to be obtained;
and identified the factors relating to pore pressure and lateral stress
change that control them.
Instrumentation for the continuous monitoring of pore pressures, lateral
stresses and wall bending
moments was developed during work on excavations for the Channel Tunnel
Rail Link (now HS1)
at Ashford, Kent, 1999-2001 [3.2]. By 2005, we had developed new
instrumentation methods for
the continuous monitoring of key stresses and stress resultants (lateral
earth pressures, pore water
pressures, prop loads and bending moments) associated with propped
embedded retaining walls
and retained excavations, and identified appropriate methods of analysis
incorporated into industry
guidance e.g. [3.3]. Richards has subsequently led the development of new
monitoring methods to
measure and understand dynamic loading events on foundations since 2002.

A significant area of development and application has been railway
infrastructure, following
EPSRC's drive in the wake of the Hatfield crash in 2000 to establish
railway-relevant research in
UK universities through Rail Research UK (a consortium of seven
universities, led jointly by
Southampton and Birmingham, with Powrie as PI and Southampton providing
expertise in
geomechanics and infrastructure) in 2003. Within and beyond RRUK,
geotechnical railway
infrastructure research at Southampton (backed by total funding of £14
million) has focused on two
strands: the design and performance of ballasted track, and earthworks
such as embankments and
cutting slopes (also applicable to roads): Powrie, Richards, Clayton
(1999ff), Clarke (1979ff), Le
Pen (2012ff), Priest (2011-3), Smethurst (2012ff)
and Zervos (2002ff). We have pursued a
scientific and holistic approach to understanding track and earthworks
behaviour, in contrast to the
generally empirical and piecemeal approach that had prevailed over much of
the previous 150
years.

Powrie and Richards, with Priest, Lock (to 2011) and Bowness (2003-6,
deceased), developed
novel instrumentation and associated data processing methods to measure
dynamic
displacements of the track and the underlying ground under load from
passing trains. Geophones
and digital image analysis were used to make measurements previously
impossible or prohibitively
expensive to obtain. These techniques were used alongside advanced
numerical modelling to
analyse the complex interactions between rails, sleepers, ballast and the
ground [3.4]. The original
paper detailing the instrumentation and its use was awarded the Thomas
Hawksley Medal by the
Institution of Mechanical Engineers in 2008 — its highest award for a
published paper — and paved
the way for industry to put the new techniques into practice.

Concurrent research has focused on instrumentation and analysis of
exemplar field sites
associated with both roads and railways, to develop quantitative
understandings of the impacts of
vegetation and climate on cutting and embankment slopes, and of the
effectiveness of stabilizing
piles. Smethurst, Clarke and Powrie have developed an analytical model
linking climate, light
vegetation, soil water content and suction alongside a benchmark dataset
of continuous records
since 2002 from a road cutting near Newbury [3.5]. A later field trial
(2006-11), funded by Network
Rail and conducted in conjunction with engineering consultants Mott
MacDonald, Arup and
GeoObservations, investigated the effects of major vegetation removal from
an embankment in
Southend and extended the analytical model to trees.

Research supported by EPSRC, the construction industry and infrastructure
owners has led to an
understanding of the various mechanisms by which discrete reinforced
concrete piles may act to
stabilize embankments and cutting slopes [3.6], and to the development of
a design method which
has been used at locations including the Ironbridge Gorge UNESCO World
Heritage Site.

[3.6]* Monitoring and analysis of the bending behaviour of discrete piles
used to stabilise a railway
embankment (2007). J A Smethurst and W Powrie. Géotechnique57(8),
doi:
10.1680/geot.2007.57.8.663

Details of the impact

Over the period 2007-09, the methods of pore pressure and bending moment
monitoring we had
developed were employed directly by the SGG to assess the performance
under variable tidal
loading of the twin-walled cofferdam for the St Germans pumping station on
the River Ouse in East
Anglia, for main contractor Costain. This was at the time the largest
excavation in Europe. Pore
pressures, bending moments and wall movements were monitoired continuously
using systems
developed and specified by SGG, and used in connection with a detailed
finite difference analysis
carried out by SGG in association with Mott MacDonald to draw up a plan
for safe working within
the cofferdam and, if necessary, controlled flooding to ensure its
stability under a potential extreme
loading event. The adoption of our research enabled the project to be
completed safely and on
time, saving an estimated £15 million but more importantly mitigating the
very real risk potentially
posed to a large section of East Anglia during an anticipated spring tide
storm surge event [5.1].

Methods developed by Richards to measure and understand dynamic loading
events on
foundations have been applied to investigate the uplift capacity of
electricity transmission tower
foundations in response to a line breakage, as part of National Grid's
campaign to assess and if
necessary upgrade their network for the effects of climate change. The
better understanding of the
dynamic uplift capacity of transmission tower foundations resulting from
the research has led to a
moratorium on strengthening, and an estimated cost saving of £5-35 million
p.a. since 2006 [5.2].

Research monitoring track-train interactions contributed to the decision
to modify the wheel profile
on the Hitachi Class 395 trains used on the High Speed 1 (HS1) line
between London and
Folkestone, which forms part of the Eurostar link to Europe. All switches
and crossings (S&C,
commonly known as "points") have sensors to indicate the position of the
blade or nose (open or
closed). The introduction of the Hitachi Class 395's — the UK's fastest
commuter trains, with a top
speed of 140 mph — caused `points flicker', whereby a sensor would
indicate the switch to be open
when it was in fact closed. As faulty S&C were responsible for both
the Potters Bar and Grayrigg
disasters, in 2010 the HS1 team asked SGG to assist in identifying the
cause of the fault. A further
issue was the susceptibility of the new trains to "hunting" (unstable
lateral oscillation of the bogies)
in tunnels, which was causing considerable passenger discomfort and alarm.
A six-month field trial,
using the novel instrumentation techniques developed at Southampton [3.4],
established that a
combination of the wheel profile and the suspension settings played a
major role in both problems,
leading to a number of Hitachi trains being fitted experimentally with
different profile wheels. These
were closely monitored over several weeks to assess the effect of the new
wheel profiles and
suspension setting on hunting and points flicker. The investigation was
carried out jointly by the
University of Southampton, the NR wheel-rail interface team, S&C
manufacturers Vossloh Cogifer,
Hitachi and the train operating company South-Eastern. Results
demonstrated the success of the
modifications, which were subsequently implemented across the entire Class
395 fleet of 174
vehicles (29 × 6 car units) [5.3]. Other studies for HS1 have included
investigations into ballast
flight, jointly with Birmingham [5.4]. In Europe, ProRail, part of Dutch
railway infrastructure owner
NS Railinfratrust, has used SGG's research (in collaboration with
Deltares) to control rising
maintenance costs by identifying true mechanisms of track deterioration to
inform appropriate long-term
remedial measures [5.5].

Most railway track, both in the UK and worldwide, is founded on ballast.
This is a traditional form of
construction, but its performance limits are increasingly being tested as
train speeds and weights
and intensity of trafficking increase. In 2006, SGG was approached by
Network Rail to investigate
areas of sporadic and unexplained ballast movement ("ballast migration")
on the UK West Coast
Main Line, apparent following the introduction of tilting trains. Reported
incidences of track and
train-wheel faults had been increasing at certain curves, owing to the
gradual migration of ballast
from the high to the low rail potentially leading to trapping of ballast
particles between the wheel
and the rail. A field investigation by the Southampton Geomechanics Group
using our track
monitoring techniques, and analysis of the results, identified the
potential causes of the problem.
Continuing work funded by Network Rail through the Future
Infrastructure Systems Strategic
Research Partnership aims to devise a range of appropriate remediation
techniques [5.6, 5.7].

Our expertise in ballasted track has been used in the design and
specification of a new, 400 km-long
railway line across the Arabian desert. Facing a maintenance bill of
millions of pounds, Etihad
Rail, the promoter and eventual operator of this new rail link in the
United Arab Emirates, were
seeking to mitigate the problem of sand ingress into the ballast reducing
the life of both trains and
track. In 2011, SGG developed laboratory test apparatus and procedures to
investigate how sand
ingress will affect the performance of the ballast bed. This led to the
award of a recently-completed
£106k research contract by the design and build contractor
Saipem-Dodsal-Tecnimont JV, the
results of which have helped shape a set of transformative track
specifications with the potential for
realising significant savings in future maintenance costs [5.8].

Monitoring and analysis of the influence of vegetation, weather and
climate on the behaviour of
infrastructure embankments and cuttings have influenced the standards that
guide industry
practice. Work in collaboration with Network Rail, LUL and Mott MacDonald
has demonstrated that
the removal of mature vegetation has the potential to destabilise some
earthworks structures
during the winter, with both the species and proximity of vegetation and
the underslope drainage
conditions having a significant influence [5.9]. SGG has developed and
validated models enabling
the interactions between these and climate/weather to be quantified. Both
Network Rail and LUL
are now using the understandings gained to identify the most appropriate
type of vegetation for
particular slopes and to define their management strategies for lineside
vegetation [5.7, 5.10].

Collaboration with Mott MacDonald led to the development of an improved
design approach for
discrete pile stabilisation of earthworks. Our research demonstrated that
piles could be spaced
further apart than previously thought, providing infrastructure owners
with substantial cost savings
through the need to install fewer piles. Savings of £2.4 million and 6
months in time have been
identified on two jobs for LUL alone, and projected cost savings of
£65-100 million over a five year
period [5.10]. Increased confidence in the approach led to its successful
use to stabilize part of the
Ironbridge Gorge UNESCO World Heritage site.

Through their engagement and leadership of RRUK, researchers at
Southampton have had a
pivotal impact on the revitalisation of railway research in UK
universities and its pull-through into
industry. Southampton academic staff were instrumental in the formation of
the successor
organisation RRUKA, now being funded and run by RSSB to act as a link
between research
organisations and the UK rail industry. We led an EPSRC Feasibility
Account, which resulted in the
development of at least six new research projects involving UK
universities and the UK rail
industry, including SUSTRAIL and SPECTRUM [5.7]. Powrie contributed to UK
Government policy
in rail through his membership of the Railway Technical Strategy Steering
Group, providing
industry-wide support and advice for the Railway Technical Strategy 2012.

Sources to corroborate the impact

Note: references to papers are in professional journals and illustrate
impact in addition to the actual
research